SRN1 Mechanism Research Articles

SmI2 catalyzed SRN1 reactions of haloarenes with acetophenone enolate ions in DMSO

Iodobenzene, 2-halopyridines (Cl, Br), 2-chloroquinoline and 1-halonaphthalenes (Cl, Br) react with acetophenone enolate ion in DMSO by the SRN1 mechanism catalyzed by SmI2.

Reactivity of 1-iodoadamantane with carbanions by the SRN1 mechanism

The photostimulated reaction of 1-iodoadamantane (1) with carbanions in DMSO has been studied. Acetone enolate ion (2a) reacted with 1 to give the substitution product (4a, 20 %) and adamantane (3, 17 %); acetophenone enolate ion (2b) gave the substitution product (4b, 65 %) in the presence of 18-crown-6. In the reaction with propiophenone enolate ion (2c), the yield was lower (27 %). Anthrone anion (5) gave good yields (75 %) of the substitution product 6. The anion of nitromethane (7) did not react with 1 under photostimulation, but in the presence of 2a or b, 87 % of 1-adamantylnitromethane (8) was obtained (entrainment reactions). Low amounts of substitution products were found with the fluorene anion and no substitution was observed with other carbanions. It is suggested that these reactions occurred by the SRN1 mechanism.By competition experiments, the following reactivity order toward 1-adamantyl radicals was determined: 2a(1.0) < 2b(11) < 7(32) < 5(80). The reactivity observed is explained on the basis of the pKa of the conjugate acid of the anions and on the changes in π energy (HOMO carbanion – SOMO radical anion intermediate) that takes place in the coupling reaction.By competition experiments of 1 and Phl toward 2b, a k1:KPhl ratio of ca. 16 was found while 1-bromoadamantane and PhBr gave a k1–BrAd:KphBr ratio of ca. 0.13. This difference can be attributed to the capacity of phenyl radicals to abstract iodine atoms from 1 giving Phl and 1-adamantyl radicals, which ultimately results in an apparent greater reactivity of 1vs. Phl.

SRN1 Arylation of Some Heterocyclic Ketene Aminals with 2,4-Dinitrohalobenzenes

Abstract the anion of heterocyclic ketene aminals 1 - 4 reacted with 2, 4-dinitrohalobenzenes 5 to give the monoarylated products 6, 7, 9 and 11 by a SRN1 mechanism. In some cases, the diarylated products 8 and 10 were also isolated.

SRN1 Based Methodology for Synthesis of 2-Substituted Nitropyridines

Abstract 2-Chloronitropyridines react with the anion of benzyl cyanide, benzotriazole, imidazole, pyrrole, and phthalimide to give the corresponding 2-substituted nitro-pyridines. The SRN1 mechanism was confirmed by EPR spectroscopy and depression of reaction rate by the addition of an inhibitor.

Catalysis by ferrous ion in nucleophilic aromatic substitution reactions

Efficient catalysis is provided by ferrous chloride in the nucleophilic aromatic substitution reaction of several aryl and heteroaryl halides with a ketone enolate ion as the nucleophile in Me2SO, to give the aryl or heteroaryl ketones in fair to good yields. The enolate ions from pinacolone, acetophenone, cyclohexanone and pentan-3-one behave successfully. A side-reaction is represented in some cases by the hydrodehalogenation of the substrate ArX, and evidence is provided for the intermediacy of both Ar˙ and Ar– species. Other significant mechanistic clues acquired include: (i) inhibition by electron and radical scavengers; (ii) entrainment of poor nucleophiles by good ones; (iii) the relative reactivity of two nucleophiles in competition experiments with Phl under Fe2+catalysis having the same value as in the experiments under both photostimulation and spontaneous initiation. All these findings are consistent with an SRN1 mechanism of substitution where ferrous ion, in combination with the nucleophile, plays an important rôle in the initiation step.

Iodide ion quenching of the photolysis of 1-iodoanthraquinone anion radical: evidence for an aryl radical–nucleophile reaction

The photolysis of 1-iodoanthraquinone anion radical in acetonitrile containing tetrabutylammonium iodide (TBA+I–) is unaffected by changes in [TBA+I–] up to 0.2 mol dm–3, confirming that the previously observed iodide ion quenching results from capture of photogenerated aryl radicals by the nucleophilic iodide, a process analogous to that in nucleophilic aromatic substitution by the SRN1 mechanism.

Differences in reactivity of stabilized carbanions with haloarenes in the initiation and propagation steps of the SRN1 mechanism in DMSO

Differences in reactivity of stabilized carbanions with haloarenes in the initiation and propagation steps of the SRN1 mechanism in DMSO

SRN1 Reactions of nucleophiles with radical clocks: Rate constants for some radical-nucleophile reactions

Treatment of o-3-(but-3-enyloxy)benzene (1) with anions −SPh, −PPh2 and −PO(OEt)2 in ammonia, acetonitrile or dimethyl sulphoxide gives both direct substitution and cyclized products. The formation of the latter confirms the intermediacy of the o-3-(but-3-enyloxy)phenyl radical (2) and confirms that the reactions follow the SRN1 pathway. The kinetics of the coupling of the aryl radical 2 were determined by comparison with the known rate of cyclization of 2. Similar experiments with the neopentyl bromide, 6-bromo-5,5-dimethylhex-1-ene, and its 3-oxa derivative also gave cyclized and uncyclized products, thus confirming that the SRN1 mechanism applies to the reactions. Approximate rate constants for the coupling of a neopentyl radical with the nucleophiles −SPh and −PPh2 have thus been determined.

ChemInform Abstract: Nucleophilic Substitution by the SRN1 Mechanism on Alkyl Halides

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Arylation of heterocyclic ketene aminals with 2,4-dinitrohalobenzenes by a radical nucleophilic substitution mechanism

The anions of heterocyclic ketene aminals reacted with 2,4-dinitrohalobenzenes to give arylated products by a radical nucleophilic substitution mechanism. The SRN1 mechanism was confirmed by EPR spectroscopy, EPR spin trapping, and by depression of the reaction rate by the addition of an inhibitor.

Radical mechanism of nucleophilic substitution on halocyclohexane systems

AbstractChlorocyclohexane does not react in the dark with diphenylphosphide ions in liquid ammonia, but it reacts under irradiation to give the substitution product. Bromocyclohexane reacts slowly in the dark, but this reaction is strongly accelerated by light, and inhibited by p‐dinitrobenzene. 3‐Bromo‐2‐tetrahydropyranyl allyl ether (used as a radical probe) reacts with diphenylphosphide ions under irradiation to give both the straightforward and the cyclized substitution products. This photostimulated reaction is also inhibited by p‐dinitrobenzene. It is suggested that the chlro‐bromocyclohexanes and related compounds react under irradiation by the SRN1 mechanism of nucleophilic substitution.

ChemInform Abstract: The Photostimulated Reaction of 1‐Iodoadamantane with Carbanionic Nucleophiles in DMSO by the SRN1 Mechanism.

ChemInform Abstract: The Photostimulated Reaction of 1‐Iodoadamantane with Carbanionic Nucleophiles in DMSO by the SRN1 Mechanism.

ChemInform Abstract: Formation and Reactions of Diorganophosphinite Ions in Liquid Ammonia. Synthesis of Triorganophosphine Oxides by the SRN1 Mechanism.

The reaction of triphenyl- and tribenzylphosphine oxides with alkali metals in liquid ammonia gave diphenyl- and dibenzylphosphinite ions, respectively, in high yields and a small amount of deoxygenated products. These ions reacted under photostimulation with aryl halides by the S RN 1 mechanism to give aryldiphenyl- and aryldibenzylphosphine oxides in good yields. With tribenzylphosphine oxide, by consecutive debenzylation with alkali metals followed by photostimulated reaction with aryl halides, all the benzylic moieties could be replaced by aromatic moieties to finally obtain unsymmetrical triarylphosphine oxides

ChemInform Abstract: Reactivity of N,N‐Dialkylamide Enolate Ions. Arylation of 1‐Methyl‐2‐pyrrolidinone Enolate Ions by the SRN1 Mechanism.

ChemInformVolume 21, Issue 25 Preparative Organic Chemistry ChemInform Abstract: Reactivity of N,N-Dialkylamide Enolate Ions. Arylation of 1-Methyl-2-pyrrolidinone Enolate Ions by the SRN1 Mechanism. R. A. ALONSO, R. A. ALONSO Dep. Quim. Org., Fac. Cienc. Quim., Univ. Nacl., 5016 Cordoba, ArgentinaSearch for more papers by this authorC. H. RODRIGUEZ, C. H. RODRIGUEZ Dep. Quim. Org., Fac. Cienc. Quim., Univ. Nacl., 5016 Cordoba, ArgentinaSearch for more papers by this authorR. A. ROSSI, R. A. ROSSI Dep. Quim. Org., Fac. Cienc. Quim., Univ. Nacl., 5016 Cordoba, ArgentinaSearch for more papers by this author R. A. ALONSO, R. A. ALONSO Dep. Quim. Org., Fac. Cienc. Quim., Univ. Nacl., 5016 Cordoba, ArgentinaSearch for more papers by this authorC. H. RODRIGUEZ, C. H. RODRIGUEZ Dep. Quim. Org., Fac. Cienc. Quim., Univ. Nacl., 5016 Cordoba, ArgentinaSearch for more papers by this authorR. A. ROSSI, R. A. ROSSI Dep. Quim. Org., Fac. Cienc. Quim., Univ. Nacl., 5016 Cordoba, ArgentinaSearch for more papers by this author First published: June 19, 1990 https://doi.org/10.1002/chin.199025083Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume21, Issue25June 19, 1990 RelatedInformation

Photostimulated reaction of 1-iodoadamantane with carbanionic nucleophiles in DMSO by the SRN1 mechanism

Photostimulated reaction of 1-iodoadamantane with carbanionic nucleophiles in DMSO by the SRN1 mechanism

Photostimulated reactions of haloarenes with benzeneselenate ions by the SRN1 mechanism. Competition between electron transfer and fragmentation of radical anion intermediates

AbstractThe photostimulated reaction of p‐iodoanisole (p‐IAn) and 2‐bromopyridine with PhSe− ions in liquid ammonia gave Ph2Se, ArSePh and Ar2Se (Ar = p‐anisyl, 2‐pyridyl) by the SRN1 mechanism. These products are formed due to the competition between two steps of the proposed mechanism, the fragmentation of the radical anion intermediate formed in the coupling of aryl radicals with the PhSe− ion, and the electron transfer from the radical anion to an electron acceptor. These photostimulated reactions were carried out in different solvents in order to study their influence on the rates of the two competing reactions. They were also studied at high concentrations of p‐haloanisoles in acetonitrile (ACN), and it was found that the straightforward substitution product AnSePh was formed only at a 2.5 M concentration of p‐IAn, 7·8 M p‐BrAn and 15·6 M p‐ClAn. The last compound did not react with the PhSe− ion at concentrations as high as 15·6 M, but the substitution reaction took place in the presence of 0·025 M p‐IAn (entrainment reaction). The relative reactivity of PhSe− vs PhS− toward 2‐quinolyl radicals was studied and it was found that PhSe− reacts 2·7 times faster than PhS− in ACN.

Formation and reactions of diorganophosphinite ions in liquid ammonia. Synthesis of triorganophosphine oxides by the SRN1 mechanism

The reaction of triphenyl- and tribenzylphosphine oxides with alkali metals in liquid ammonia gave diphenyl- and dibenzylphosphinite ions, respectively, in high yields and a small amount of deoxygenated products. These ions reacted under photostimulation with aryl halides by the S RN 1 mechanism to give aryldiphenyl- and aryldibenzylphosphine oxides in good yields. With tribenzylphosphine oxide, by consecutive debenzylation with alkali metals followed by photostimulated reaction with aryl halides, all the benzylic moieties could be replaced by aromatic moieties to finally obtain unsymmetrical triarylphosphine oxides

Reactivity of N,N-dialkylamide enolate ions. Arylation of 1-methyl-2-pyrrolidinone enolate ions by the SRN1 mechanism

Photoaddition d'iodo arenes sur le methyl-1 pyrrolidinolate-2. Obtention d'aryl-3 methyl-1 pyrrolidones-2

ChemInform Abstract: Photostimulated Reactions of Neopentyl Halides with Nucleophiles by the SRN1 Mechanism.

AbstractThe neopentyl halides (I), (IV), or (XI) are irradiated in the presence of various nucleophiles, e.g. sodium diphenylphosphide, potassium arsenide, both generated in situ, or sodium selenide (XII), to yield the corresponding substitution products as shown in the reaction scheme.

The SRN1 mechanism as a route to nucleophilic substitution on alkyl halides

A series of haloaliphatic compounds that react with nucleophiles by the SRN1 mechanism due to steric, electronic, or strain factors.